Reference is made to Applicant's two commonly assigned applications filed simultaneously herewith corresponding to Finnish applications FI 892264 AND FI 892265 and having the same title as this application.
The present invention concerns a method and apparatus for manufacturing a fibre-reinforced material. Specifically the present invention concerns a method and apparatus for manufacturing fibre-reinforced material, which is formed by reinforcing a fibre bundle or bundles bonded with a matrix forming resin material in such a way that the individual fibres are surrounded by resin material.
The main problem in the manufacture of products of this kind is the high viscosity of some matrix forming materials. Because the individual fibres in the fibre bundles are very closely near to each other, it is thereby difficult for the resin material to penetrate into the fibre bundle to surround all individual fibres. However, such penetration is necessary in view of the desired properties of the product, such as strength, stiffness, chemical resistance etc.
Many methods have been tried to solve the problem. In one solution fibre bundles are transferred through a so-called cross-head die, in which molten or liquid resin is penetrated into the fibre bundles moving through the die. In the so-called powder method a web of fibre bundles is transferred through a bed of thermoplastic resin particles, whereby the fibre bundles carries along resin particles, which at a later stage are melted. Known also are solvent methods in which fiber bundles are impregnated with resins dissolved in a liquid medium.
The cross-head die method has proven to be ineffective in the impregnation of fibre bundles with thermoplastic resin because all individual fibres will not be surrounded by resin material. Powder methods necessitate a multiplicity of processing stages which are difficult to synchronize, are expensive to purchase and operate while damaging the reinforcement. In solvent methods a drying process is required, which is expensive, causes environmental problems, is time-consuming and limits the production rate. Furthermore the quality of the product is low due to voids left after the removal of solvents.